Semiconductor package structure

ABSTRACT

A semiconductor package structure is provided. The semiconductor package structure includes a substrate having a first surface and a second surface opposite thereto. The substrate includes a wiring structure. The semiconductor package structure also includes a first semiconductor die disposed over the first surface of the substrate and electrically coupled to the wiring structure. The semiconductor package structure further includes a second semiconductor die disposed over the first surface of the substrate and electrically coupled to the wiring structure. The first semiconductor die and the second semiconductor die are separated by a molding material. In addition, the semiconductor package structure includes a first hole and a second hole formed on the second surface of the substrate.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 62/470,915 filed on Mar. 14, 2017, the entirety of which is incorporated by reference herein.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a semiconductor package structure, and in particular to a semiconductor package structure with holes formed on a top surface of a substrate therein.

Description of the Related Art

A semiconductor package can not only provide a semiconductor die with protection from environmental contaminants, but it can also provide an electrical connection between the semiconductor die packaged therein and a substrate, such as a printed circuit board (PCB). For instance, a semiconductor die may be enclosed in an encapsulating material, and traces are electrically connected to the semiconductor die and the substrate.

However, a problem with such a semiconductor package is that it is subject to different temperatures during the packaging process. The semiconductor package may be highly stressed due to the different coefficients of thermal expansion (CTEs) of the various substrate and semiconductor die materials. As a result, the semiconductor package may exhibit warping or cracking so that the electrical connection between the semiconductor die and the substrate may be damaged, and the reliability of the semiconductor package may be decreased.

This problem is exacerbated in the case of a relatively large package, for example a package of 50 mm×50 mm or larger. Therefore, a novel semiconductor package structure is desirable.

BRIEF SUMMARY OF THE INVENTION

Semiconductor package structures are provided. An exemplary embodiment of a semiconductor package structure includes a substrate having a first surface and a second surface opposite thereto. The substrate includes a wiring structure. The semiconductor package structure also includes a first semiconductor die disposed over the first surface of the substrate and electrically coupled to the wiring structure. The semiconductor package structure further includes a second semiconductor die disposed over the first surface of the substrate and electrically coupled to the wiring structure. The first semiconductor die and the second semiconductor die are separated by a molding material. In addition, the semiconductor package structure includes a first hole and a second hole formed on the second surface of the substrate.

Another exemplary embodiment of a semiconductor package structure includes a substrate having a wiring structure. The semiconductor package structure also includes a first semiconductor die disposed over the substrate and electrically coupled to the wiring structure. The semiconductor package structure further includes a second semiconductor die disposed over the substrate and electrically coupled to the wiring structure. The first semiconductor die and the second semiconductor die are arranged side-by-side. In addition, the semiconductor package structure includes a plurality of holes formed on a surface of the substrate. The holes are located within projections of the first semiconductor die and the second semiconductor die on the substrate.

Yet another exemplary embodiment of a substrate structure includes a wiring structure disposed in a substrate, wherein the wiring structure is coupled to a plurality of semiconductor dies disposed over the substrate. The substrate structure also includes a plurality of holes formed on a surface of the substrate, wherein the holes are located within projections of the semiconductor die on the substrate.

A detailed description is given in the following embodiments with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:

FIG. 1A is a cross-sectional view of a semiconductor package structure, in accordance with some embodiments of the disclosure;

FIG. 1B is a cross-sectional view of a semiconductor package structure, in accordance with some other embodiments of the disclosure;

FIG. 1C is a plan view of an arrangement of holes in a substrate of the semiconductor package structure shown in FIG. 1A, and FIG. 1A is a cross-sectional view of the semiconductor package structure along line I-I′ of FIG. 1C;

FIGS. 2A-2B are plan views showing shapes of holes in substrates of semiconductor package structures, in accordance with some embodiments of the disclosure;

FIGS. 3A-3B are plan views showing arrangements of holes in substrate of semiconductor package structures, in accordance with some embodiments of the disclosure; and

FIGS. 4A-4B are plan views showing locations of holes in substrates of semiconductor package structures, in accordance with some embodiments of the disclosure.

DETAILED DESCRIPTION OF THE INVENTION

The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is determined by reference to the appended claims.

The present invention will be described with respect to particular embodiments and with reference to certain drawings, but the invention is not limited thereto and is only limited by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated for illustrative purposes and not drawn to scale. The dimensions and the relative dimensions do not correspond to actual dimensions in the practice of the invention.

FIG. 1A is a cross-sectional view of a semiconductor package structure 100 a, in accordance with some embodiments of the disclosure. FIG. 1C is a plan view of an arrangement of holes in a substrate 101 of the semiconductor package structure 100 a shown in FIG. 1A, and FIG. 1A is a cross-sectional view of the semiconductor package structure 100 a along line I-I′ of FIG. 1C.

Additional features can be added to the semiconductor package structure 100 a. Some of the features described below can be replaced or eliminated for different embodiments. To simplify the diagram, only a portion of the semiconductor package structure 100 a is depicted in FIGS. 1A and 1C. In some embodiments, the semiconductor package structure 100 a may include a wafer-level semiconductor package, for example, a flip-chip semiconductor package.

Referring to FIG. 1, the semiconductor package structure 100 a may be mounted on a base (not shown). In some embodiments, the semiconductor package structure 100 a may be a system-on-chip (SOC) package structure. Moreover, the base may include a printed circuit board (PCB) and may be formed of polypropylene (PP). In some embodiments, the base may include a package substrate. The semiconductor package structure 100 a is mounted on the base by a bonding process. For example, the semiconductor package structure 100 a includes bump structures 111. In some embodiments, the bump structures 111 may be conductive ball structures (such as ball grid array (BGA)), conductive pillar structures, or conductive paste structures that are mounted on and electrically coupled to the base by the bonding process.

In the embodiment, the semiconductor package structure 100 a includes a substrate 101. The substrate 101 has a wiring structure therein. In some embodiments, the wiring structure in the substrate 101 is a fan-out structure, and may include one or more conductive pads 103, conductive vias 105, conductive layers 107 and conductive pillars 109. In such cases, the wiring structure in the substrate 101 may be disposed in one or more inter-metal dielectric (IMD) layers. In some embodiments, the IMD layers may be formed of organic materials, which include a polymer base material, non-organic materials, which include silicon nitride (SiN_(x)), silicon oxide (SiO_(x)), grapheme, or the like. For example, the IMD layers are made of a polymer base material. It should be noted that the number and configuration of the IMD layers, the conductive pads 103, the conductive vias 105, the conductive layers 107 and the conductive pillars 109 shown in Figures and only some examples and are not limitations to the present invention.

Moreover, the semiconductor package structure 100 a also includes a first semiconductor die 115 a and a second semiconductor die 115 b bonded onto the substrate 101 through a plurality of conductive structures 119. The substrate 101 has a first surface 101 a and a second surface 101 b opposite thereto, the first surface 101 a is facing the first semiconductor die 115 a and the second semiconductor die 115 b, and the second surface 101 b is facing the above-mentioned base. The conductive structures 119 are disposed over the first surface 101 a and below the first semiconductor die 115 a and the second semiconductor die 115 b, and the bump structures 111 are disposed over the second surface 101 b of the substrate 101.

In some embodiments, the first semiconductor die 115 a and the second semiconductor die 115 b are electrically coupled to the bump structures 111 through the conductive structures 119 and the wiring structure in the substrate 101. In addition, the conductive structures 119 may be controlled collapse chip connection (C4) structures. It should be noted that the number of semiconductor dies integrated in the semiconductor package structure 100 a is not limited to that disclosed in the embodiment.

In some embodiments, the first semiconductor die 115 a and the second semiconductor die 115 b are active devices. For example, the first semiconductor die 115 a and the second semiconductor die 115 b may be logic dies including a central processing unit (CPU), a graphics processing unit (GPU), a dynamic random access memory (DRAM) controller or any combination thereof. In some other embodiments, one or more passive devices are also bonded onto the substrate 101.

The first semiconductor die 115 a and the second semiconductor dies 115 b are arranged side-by-side. In some embodiments, the first semiconductor die 115 a and the second semiconductor dies 115 b are separated by a molding material 117. The molding material 117 surrounds the first semiconductor die 115 a and the second semiconductor die 115 b, and adjoins the sidewalls of the first semiconductor die 115 a and the second semiconductor die 115 b. In some embodiments, the molding material 117 includes a nonconductive material such as an epoxy, a resin, a moldable polymer, or another suitable molding material. In some embodiments, the molding material 117 is applied as a substantial liquid, and then is cured through a chemical reaction. In some other embodiments, the molding material 117 is an ultraviolet (UV) or thermally cured polymer applied as a gel or malleable solid, and then is cured through a UV or thermal curing process. The molding material 117 may be cured with a mold (not shown).

In some embodiments, the surfaces of the first semiconductor die 115 a and the second semiconductor dies 115 b facing away from the first surface 101 a of the substrate 101 are exposed by the molding material 117, such that a heat dissipating device (not shown) can directly attached to the surfaces of the first semiconductor die 115 a and the second semiconductor dies 115 b. As a result, the heat-dissipation efficiency of the semiconductor package structure 100 a can be improved, particularly for a large semiconductor package structure, such as 50 mm×50 mm, which is preferred for high power applications.

The semiconductor package structure 100 a also includes a polymer material 121 disposed under the molding material 117, the first semiconductor die 115 a and the second semiconductor die 115 b, and between the conductive structures 119. The semiconductor package structure 100 a further includes an underfill layer 123 interposed between the first surface 101 a of the substrate 101 and the polymer material 121. In some embodiments, the first semiconductor die 115 a, the second semiconductor dies 115 b and the molding material 117 are surrounded by the underfill layer 123. The polymer material 121 and the underfill layer 123 are disposed to compensate for differing coefficients of thermal expansion (CTEs) between the substrate 101, the conductive structures 119, the first semiconductor die 115 a and the second semiconductor dies 115 b.

In addition, the semiconductor package structure 100 a includes a frame 113 attached to the first surface 101 a of the substrate 101 through an adhesive layer 112. The first semiconductor die 115 a and the second semiconductor die 115 b are surrounded by the frame 113 and the adhesive layer 112. In some embodiments, the frame 113 and the adhesive layer 112 are separated from the underfill layer 121 by a gap. The substrate 101 has a first edge 101E₁ and a second edge 101E₂ opposite thereto. In some embodiments, the first edge 101 E₁ and the second edge 101E₂ are coplanar with sidewalls of the frame 113 and the adhesive layer 112.

Still referring to FIG. 1A, the substrate 101 of the semiconductor package structure 100 a includes a first hole 110 a and a second hole 110 b formed on the second surface 101 b. In some embodiments, at least one of the first hole 110 a and the second hole 110 b penetrates through the substrate 101 from the first surface 101 a to the second surface 101 b. Although the first hole 110 a and the second hole 110 b shown in FIG. 1A penetrate through the substrate 101, in some other embodiments, both the first hole 110 a and the second hole 110 b do not penetrate through the substrate 101 from the first surface 101 a to the second surface 101 b. In some embodiments, the first hole 110 a is covered by the first semiconductor die 115 a, and the second hole 110 b is covered by the second semiconductor die 115 b. In other words, the first hole 110 a is located within the projection of the first semiconductor die 115 a on the substrate 101, and the second hole 110 b is located within the projection of the second semiconductor die 115 b on the substrate 101.

Specifically, the first semiconductor die 115 a and the second semiconductor die 115 b have a center line C-C′ between them. The first hole 110 a is disposed closer to the center line C-C′ than the first edge 101E₁ of the substrate 101, and the second hole 110 b is disposed closer to the center line C-C′ than the second edge 101E₂ of the substrate 101. Although there are only two holes in the substrate 101 shown in FIG. 1A, it should be noted that there is no limitation on the number of the holes formed in the substrate 101.

In some embodiments, the first hole 110 a and the second hole 110 b are formed by a laser drilling process or another suitable process. It should be noted that the first hole 110 a and the second hole 110 b may be formed by the same forming process for the conductive pillars 109 in the wiring structure of the substrate 101. Moreover, the first semiconductor die 115 a and the second semiconductor die 115 b are bonded to the substrate 101 after forming the holes in the substrate 101. Therefore, the damage of the first semiconductor die 115 a and the second semiconductor die 115 b can be prevented.

Referring to FIG. 1C, which is a plan view of an arrangement of holes in a substrate 101 of the semiconductor package structure 100 a shown in FIG. 1A, and FIG. 1A is a cross-sectional view of the semiconductor package structure 100 a along line I-I′ of FIG. 1C. It should be noted that FIG. 1C is the plan view from the bottom of the semiconductor package structure 100 a. In other words, FIG. 1C is the plan view from the second surface 101 b of the substrate 101, which the bump structures 111 are disposed on. In particular, the bump structures 111 are omitted for brevity.

As shown in FIG. 1C, the substrate 101 includes more than two holes. In particular, the substrate 101 further includes a third hole 110 c and the fourth hole 110 d formed on the second surface 101 b. The third hole 110 c is covered by the first semiconductor die 115 a, and the fourth hole 110 d is covered by the second semiconductor die 115 b. It should be noted that the substrate 101 has a center 101C, and the first hole 101 a, the second hole 101 b, the third hole 110 c, and the fourth hole 110 d are disposed closer to the center 101C than the first edge 101E₁ and the second edge 101E₂ of the substrate 101.

The holes formed in the substrate 101, for example, the first hole 110 a, the second hole 110 b, the third hole 110 c and the fourth hole 110 d, are designed to release the stress in the substrate 101, especially the stress concentrated in the region below the interface between two semiconductor dies (i.e. the first semiconductor die 115 a and the second semiconductor die 115 b). Since the semiconductor package structure 100 a may be highly stressed due to the different coefficients of thermal expansion (CTEs) of the substrate 101 and the semiconductor dies, the holes formed in the substrate 101 can solve the warping or cracking problems caused by mismatched CTEs. As a result, the electrical connection within the semiconductor package structure 100 a may not be damaged, and the reliability of the semiconductor package structure 100 a may be increased.

FIG. 1B is a cross-sectional view of a semiconductor package structure 100 b, in accordance with some other embodiments of the disclosure. Descriptions of elements of the embodiments hereinafter that are the same as or similar to those previously described with reference to FIG. 1A are omitted for brevity.

As shown in FIG. 1B, the semiconductor package structure 100 b includes a stress buffer layer 125 filled in the first hole 110 a and the second hole 110 b. The stress buffer layer 125 is made of a polymer material, such as a silicone resin or rubber. In some embodiments, the stress buffer layer 125 is made of an organic resin, such as Ajinomoto Build-up Film (ABF).

Moreover, the stress buffer layer 125 may be formed by a spin coating process. In some other embodiments, a material of the stress buffer layer 125 may be dispensed in the first hole 110 a and the second hole 110 b, and an excess portion of the material of the stress buffer layer 125 may be removed. In some embodiments, the stress buffer layer 125 may be formed before bonding the first semiconductor die 115 a and the second semiconductor die 115 b to the substrate 101.

In some embodiments, the stress buffer layer 125 may filled up the first hole 110 a and the second hole 110 b, and the surfaces of the stress buffer layer 125 are level with the second surface 101 b of the substrate 101. In some other embodiments, the surfaces of the stress buffer layer 125 may not be level with the second surface 101 b of the substrate 101 according to the actual manufacturing processes.

Filling the first hole 110 a and the second hole 110 b with the stress buffer layer 125 may offer advantages like preventing the impurities and dusts from dropping into the first hole 110 a and the second hole 110 b during the handling process of the substrate 101. In addition, the warping or cracking problems caused by mismatched coefficients of thermal expansion in the semiconductor package structure 100 b can be solved by the holes (including the first hole 110 a and the second hole 110 b) and the stress buffer layer 125 formed in the substrate 101. Accordingly, the electrical connection within the semiconductor package structure 100 b may not be damaged, and the lifespan of the semiconductor package structure 100 b may be increased.

FIG. 2A is a plan view showing shapes of holes in a substrate 201A of a semiconductor package structure 200 a, and FIG. 2B is a plan view showing shapes of holes in a substrate 201B of a semiconductor package structure 200 b, in accordance with some embodiments of the disclosure. Descriptions of elements of the embodiments hereinafter that are the same as or similar to those previously described with reference to FIG. 1C are omitted for brevity.

Referring to FIG. 2A, the semiconductor package structure 200 a has holes A, B, C, D, E, F, G, H, I, J, K and L in the substrate 201A, and the number of holes in the substrate 201A is much more than that in the substrate 101 of the semiconductor package structure 100 a. As shown in FIG. 2A, the holes A, B, C, D, E and F are covered by the first semiconductor die 115 a, and the holes G, H, I, J, K and L are covered by the second semiconductor die 115 b. In other words, the holes A-F are located within the projection of the first semiconductor die 115 a on the substrate 201A, and the holes G-L are located within the projection of the second semiconductor die 115 b on the substrate 201A.

Specifically, the holes A, B and C are arranged in a first array, the holes D, E and F are arranged in a second array, the holes G, H and I are arranged in a third array, and the holes J, K and L are arranged in a fourth array. The first array, the second array, the third array and the fourth array are parallel to the center line C-C′ of the first semiconductor die 115 a and the second semiconductor die 115 b.

Referring to FIG. 2B, the substrate 201B in the semiconductor package structure 200 b has holes a, b, c, d, e, f, g, h, i, j, k and l, which are arranged in the same way as the holes A-L of the substrate 201A in the semiconductor package structure 200 a. The difference between the substrate 201A and the substrate 201B is that the holes a-l have circular shapes in the plan view. Compared with the holes A-L in the substrate 201A, which have rectangular shapes in the plan view, the problems of stress concentrated at the corners of the holes A-L can be prevented in the substrate 201B due to the round shapes of the holes a-l. Therefore, the probability that the cracking problem occurs in the substrate 201B of the semiconductor package structure 200 b can be more decreased.

In some embodiments, stress buffer layers may be optionally formed in the holes A-L of the semiconductor package structure 200 a and in the holes a-l of the semiconductor package structure 200 b. It should be noted that the holes A-L are symmetrically located about the center line C-C′ in the plan view of FIG. 2A, and the holes a-l are symmetrically located about the center line C-C′ in the plan view of FIG. 2B. In some other embodiments, the holes A-L are symmetrically located about the center 201C of the substrate 201A in the plan view of FIG. 2A, and the holes a-l are symmetrically located about the center 201C′ of the substrate 201B in the plan view of FIG. 2B.

FIG. 3A is a plan view showing arrangements of holes in a substrate 301A of a semiconductor package structure 300 a, and FIG. 3B is a plan view showing arrangements of holes in a substrate 301B of a semiconductor package structure 300 b, in accordance with some embodiments of the disclosure. Descriptions of elements of the embodiments hereinafter that are the same as or similar to those previously described with reference to FIG. 2A are omitted for brevity.

Referring to FIG. 3A, the semiconductor package structure 300 a has holes A, B, C, D, E, and F in the substrate 301A. The holes A, B and C are covered by the first semiconductor die 115 a, and the holes D, E and F are covered by the second semiconductor die 115 b. In other words, the holes A-C are located within the projection of the first semiconductor die 115 a on the substrate 301A, and the holes D-F are located within the projection of the second semiconductor die 115 b on the substrate 301A.

It should be noted that the holes A-F are arranged radially around the center 301C of the substrate 301A. In some other embodiments, the holes A-F are arranged radially around a center, and the center is located between the first semiconductor die 115 a and the second semiconductor die 115 b.

Compared with the semiconductor substrate 200 a of FIG. 2A, the stress in the substrate 301A of the semiconductor package structure 300 a, which has holes A-F arranged radially, can be released more efficiently. In other words, in order to obtain the same stress releasing effect as in the semiconductor package structure 200 a, the number of the holes in the substrate 301A of the semiconductor package structure 300 a can be less than the number of the holes in the substrate 201A of the semiconductor package structure 200 a. However, the substrate 201A of the semiconductor package structure 200 a, which has holes A-L arranged parallel to the center line C-C′, is more easily to be manufactured than the substrate 301A of the semiconductor package structure 300 a, which has holes A-F arranged radially.

Referring to FIG. 3B, the substrate 301B in the semiconductor package structure 300 b has holes a, b, c, d, e, f, g, h, i, j, k, 1, m and n arranged staggered in the substrate 301B. Specifically, the holes a-g are covered by the first semiconductor die 115 a and staggered disposed along the direction of the center line C-C′, and the holes h-n are covered by the second semiconductor die 115 b and staggered disposed along the direction of the center line C-C′.

Compared with the semiconductor package structure 200 a in FIG. 2A and the semiconductor package structure 300 a in FIG. 3A, the substrate 301B of the semiconductor package structure 300 b can combine the above-mentioned benefits of the hole arrangements of the substrate 201A in the semiconductor package structure 200 a and the substrate 301A of the semiconductor package structure 300 a. Specifically, the holes a-n in the substrate 301B can be manufactured easily, and the stress in the substrate 301B can be released efficiently.

In some embodiments, stress buffer layers may optionally be formed in the holes A-F of the semiconductor package structure 300 a and the holes a-n of the semiconductor package structure 300 b. It should be noted that the holes A-F are symmetrically located about the center line C-C′ in the plan view of FIG. 3A, and the holes a-n are symmetrically located about the center line C-C′ in the plan view of FIG. 3B. In some other embodiments, the holes A-F are symmetrically located about the center 301C of the substrate 301A in the plan view of FIG. 3A, and the holes a-n are symmetrically located about the center 301C′ of the substrate 301B in the plan view of FIG. 3B.

FIG. 4A is a plan view showing locations of holes in a substrate 401A of a semiconductor package structure 400 a, and FIG. 4B is a plan view showing locations of holes in a substrate 401B of a semiconductor package structure 400 b, in accordance with some embodiments of the disclosure. Descriptions of elements of the embodiments hereinafter that are the same as or similar to those previously described with reference to FIG. 2A are omitted for brevity.

Referring to FIG. 4A, the substrate 401A in the semiconductor package structure 400 a has holes A, B, C, D, E, F, G, H, I, J, K and L arranged in the same way as the holes A-L of the substrate 201A in the semiconductor package structure 200 a shown in FIG. 2A. The holes A-L are arranged parallel to the center line C-C′ in the substrate 401A. The difference between FIGS. 2A and 4A is that the holes A-L in the substrate 401A are located closer to the center 401C of the substrate 401A than the holes A-L in the substrate 201A.

Since the maximum stress is likely to be concentrated at the center 401C of the substrate 401A, the stress in the substrate 401A of the semiconductor package structure 400 a, which has holes A-L located closer to the center 401C of the substrate 401A, can be released more efficiently than the semiconductor package structure 200 a.

Referring to FIG. 4B, the substrate 401B in the semiconductor package structure 400 b has holes a, b, c, d, e, f, g, h, i and j located along the peripheral edge of the substrate 401B. In other words, the holes a-j are located far from the center 401C′ of the substrate 401B to reserve space in the middle of the substrate 401B for routing. Compared with the semiconductor substrate 400 a of FIG. 4A, the semiconductor substrate 400 b of FIG. 4B can provide a better routing capability for the substrate 401B.

In some embodiments, stress buffer layers may optionally be formed in the holes A-L of the semiconductor package structure 400 a and the holes a-j of the semiconductor package structure 400 b. It should be noted that the holes A-L are symmetrically located about the center line C-C′ in the plan view of FIG. 4A, and the holes a-j are symmetrically located about the center line C-C′ in the plan view of FIG. 4B. In some other embodiments, the holes A-L are symmetrically located about the center 401C of the substrate 401A in the plan view of FIG. 4A, and the holes a-j are symmetrically located about the center 401C′ of the substrate 401B in the plan view of FIG. 4B.

According to the foregoing embodiments, the holes formed in the substrate are designed to release the stress in the substrate, especially the stress concentrated in the region below the interface between two semiconductor dies. Since the semiconductor package structure may be highly stressed due to the different coefficients of thermal expansion (CTEs) of the substrate and the semiconductor dies, the holes formed in the substrate can solve the warping or cracking problems caused by mismatched CTEs. As a result, the electrical connection within the semiconductor package structure may not be damaged, and the reliability and the lifespan of the semiconductor package structure may be increased.

Many variations and/or modifications can be made to embodiments of the disclosure. The semiconductor package structures in accordance with some embodiments of the disclosure can be used to form a three-dimensional (3D) package, a 2.5D package, a fan-out package, or another suitable package. In addition, the arrangements, the shapes, and the locations of the holes in the substrate can be adjusted according to the types of the application.

While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements. 

What is claimed is:
 1. A semiconductor package structure, comprising: a substrate having a first surface and a second surface opposite thereto, wherein the substrate comprises a wiring structure; a first semiconductor die disposed over the first surface of the substrate and electrically coupled to the wiring structure; a second semiconductor die disposed over the first surface of the substrate and electrically coupled to the wiring structure, wherein the first semiconductor die and the second semiconductor die are separated by a molding material; and a first hole and a second hole formed on the second surface of the substrate.
 2. The semiconductor package structure as claimed in claim 1, wherein the first hole is covered by the first semiconductor die, and the second hole is covered by the second semiconductor die.
 3. The semiconductor package structure as claimed in claim 1, wherein the first hole and the second hole are disposed closer to a center line between the first semiconductor die and the second semiconductor die than an edge of the substrate.
 4. The semiconductor package structure as claimed in claim 1, wherein the first hole and the second hole have rectangular shapes or circular shapes from a plan view.
 5. The semiconductor package structure as claimed in claim 1, further comprising: a third hole and a fourth hole formed on the second surface of the substrate, wherein the third hole is covered by the first semiconductor die, and the fourth hole is covered by the second semiconductor die, and wherein the first hole, the second hole, the third hole and the fourth hole are arranged radially around a center of the substrate.
 6. The semiconductor package structure as claimed in claim 1, further comprising: a third hole and a fourth hole formed on the second surface of the substrate, wherein the third hole is covered by the first semiconductor die, and the fourth hole is covered by the second semiconductor die, and wherein the first hole and the third hole are arranged in a first array, and the second hole and the fourth hole are arranged in a second array, the first array and the second array are parallel to a center line between the first semiconductor die and the second semiconductor die.
 7. The semiconductor package structure as claimed in claim 6, further comprising: a fifth hole and a sixth hole formed on the second surface of the substrate, wherein the fifth hole is covered by the first semiconductor die, and the sixth hole is covered by the second semiconductor die, and wherein the first hole, the third hole and the fifth hole are staggered along a direction of the center line, and the second hole, the fourth hole and the sixth hole are staggered along the direction of the center line.
 8. The semiconductor package structure as claimed in claim 1, further comprising; a plurality of conductive structures disposed over the first surface and below the first semiconductor die and the second semiconductor die; and a plurality of bump structures disposed over the second surface of the substrate, wherein the first semiconductor die and the second semiconductor die are electrically coupled to the bump structures through the conductive structures and the wiring structure in the substrate.
 9. The semiconductor package structure as claimed in claim 1, further comprising: a frame disposed over the first surface of the substrate, wherein the frame surrounds the first semiconductor die and the second semiconductor die.
 10. The semiconductor package structure as claimed in claim 1, wherein the molding material further surrounds the first semiconductor die and the second semiconductor die, and surfaces of the first semiconductor die and the second semiconductor die facing away from the substrate are exposed by the molding material.
 11. The semiconductor package structure as claimed in claim 1, further comprising: a stress buffer layer filled into the first hole and the second hole.
 12. A semiconductor package structure, comprising: a substrate having a wiring structure; a first semiconductor die disposed over the substrate and electrically coupled to the wiring structure; a second semiconductor die disposed over the substrate and electrically coupled to the wiring structure, wherein the first semiconductor die and the second semiconductor die are arranged side-by-side; and a plurality of holes formed on a surface of the substrate, wherein the holes are located within projections of the first semiconductor die and the second semiconductor die on the substrate.
 13. The semiconductor package structure as claimed in claim 12, wherein the holes have rectangular shapes or circular shapes from a plan view.
 14. The semiconductor package structure as claimed in claim 12, wherein the holes are arranged in arrays that are parallel to a center line between the first semiconductor die and the second semiconductor die.
 15. The semiconductor package structure as claimed in claim 12, wherein the holes are arranged radially around a center, and the center is located between the first semiconductor die and the second semiconductor die.
 16. The semiconductor package structure as claimed in claim 12, wherein the holes are staggered along a direction parallel to a center line between the first semiconductor die and the second semiconductor die.
 17. The semiconductor package structure as claimed in claim 12, wherein the holes are located close to a center of the substrate.
 18. The semiconductor package structure as claimed in claim 12, wherein the holes are located along a peripheral edge of the substrate.
 19. The semiconductor package structure as claimed in claim 12, wherein the holes are symmetrically located about a center line between the first semiconductor die and the second semiconductor die.
 20. The semiconductor package structure as claimed in claim 12, further comprising: a stress buffer layer filled into the holes, wherein the stress buffer layer is made of a polymer material.
 21. A substrate structure, comprising: a wiring structure disposed in a substrate, wherein the wiring structure is coupled to a plurality of semiconductor dies disposed over the substrate; and a plurality of holes formed on a surface of the substrate, wherein the holes are located within projections of the semiconductor dies on the substrate. 